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Codiode/Problems/Sequential Logic

JK Flip-Flop with Synchronous Enable

MediumLogic CircuitBuild

Control logic often requires state elements that update only on specific cycles without interrupting the global clock tree. The synchronous enable pattern allows a flip-flop to hold its state or accept new inputs based on a control signal, avoiding the severe timing hazards introduced by clock gating.

The circuit must behave as a standard JK flip-flop when EN is 1, and completely hold its current state when EN is 0, regardless of the values on J and K.

| EN | J | K | Q | Q_next | |------|-----|-----|-----|----------| | 0 | 1 | 1 | 0 | 0 | | 0 | 1 | 1 | 1 | 1 | | 1 | 0 | 0 | 0 | 0 | | 1 | 0 | 0 | 1 | 1 | | 1 | 0 | 1 | 0 | 0 | | 1 | 0 | 1 | 1 | 0 | | 1 | 1 | 0 | 0 | 1 | | 1 | 1 | 0 | 1 | 1 | | 1 | 1 | 1 | 0 | 1 | | 1 | 1 | 1 | 1 | 0 |

Constraints

  • Do not connect EN to the clock signal.
  • Gate the J and K inputs using combinational logic.
  • Drive the Q output using a single JK flip-flop.

Topics

Sequential LogicLatches and Flip-FlopsClocking

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